Analysis of Heavy Metal Concentrations in Waste Water

Heavy metal contamination of water has become an important problem in recent years. Most hazardous heavy metals exist in environmental water in trace or ultra-trace amounts, which requires establishing highly sensitive analytical methods. In this research, quantitative analyses were performed using atomic absorption spectrometry to determine Fe, Cd, Pb, Cr and Ni levels in industrial effluents. Water pollution caused by heavy metal ions is becoming a serious threat to human and aquatic lives day by day.

Therefore, the treatment of heavy metal is of special concern for environmental scientists and engineers. The present work focus on heavy metals in the industrial water samples was collected from five industrial zones of chittoor district and analyzed for the concentrations of Fe, Cd, Pb, Cr and Ni. The concentrations of Fe, Cd, Pb, Cr and Ni were analyzed with the help of Atomic Absorption Spectrometry (AAS). The levels of Fe, Cd, Pb, Cr and Ni in the studied Industrial waste water ranges from (1.12-1.36, 0.076-1.16, 0.1-1.07, 0.65-2.8, 0.14-2.24) mg/L respectively.

From these concentrations, the concentration obtained for Cr, Cd and Pb were greater than the concentration reported by World Health Organization (WHO). This shows that the presence of Ni, Fe, Cr, Cd and Pb in the study area has a significant influence to health. Especially, Cd, Cr, Fe and Pb exhibited high significance toxicity effect even at lower concentration. The chemical parameters such as electrical conductivity, pH and hardness were also measured. To conclude, the variation in water flow and the anthropogenic activities were the main reasons for this water pollution.

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Introduction

Water contamination from heavy metal ions constitutes a severe environmental problem in many countries today. Water is the elixir of life that cannot be substituted by any other resource. For the most part of the water is now getting polluted. There are currently many sources of heavy metal contaminations coming from a variety of industrial processes in for example by the discharge of domestic or urban sewage, manufacturing of battery, smelting industries [1], steel and iron, chemicals, plastics, textile, fertilizer, food and beverages, breweries, pharmaceuticals, soap, petroleum and petrochemical, automobile, paper mill, tannery and cosmetics, tobacco, agricultural wastes and paint industries.

The presence of these metals in industrial waste water constitutes serious environmental problems due to their non-biodegradable properties and toxicity. The three major release paths of heavy metal ions are: industrial effluents that are not filtered properly, air pollutions as in the case of combustions, or leakage from used products containing heavy metals, for example batteries, paints or metal finishing.

Many of the aforementioned paths end up as water contaminations either as direct release into open bodies of water, e.g. lakes, streams or ocean, in the case of industrial effluents or by atmospheric deposition directly on open water surfaces. Atmospheric depositions on vegetation, buildings or other surfaces can be washed away by rain and will either reach the ground water or be accumulated in the soil. Atmospheric depositions in cities can also be washed out to lakes or streams as urban run-off if not properly handled. Some of the most commonly used heavy metals that give rise to environmental problems are lead, chromium cadmium and nickel.

Some examples of applications that specifically use lead, cadmium, chromium and nickel are: battery industries, mining, paint, welding, solders, metal plating, electroplating and gasoline. Divalent heavy metal ions such as Pb(II), Cd(II) and Ni(II) have been shown to have high toxicity effects, both long term and short term, on both human and aquatic life. The short term effects are often acute poising while the long term effects have a wide range including cancerogenic effects.

The long term toxicity effects start at low concentration as the metal ions accumulates in organisms and are persistent in biological systems. The toxicity concentrations of many heavy metal ions are well below the current permissible limits of many countries today. It is therefore in the public interest to reduce the contamination of heavy metal ions both from industrial effluents and emission sources.

Metals occur naturally in the earth's crust, and their contents in the environment can vary between different regions resulting in spatial variations of background concentrations. Metals are substances with high electrical conductivity, rigidity, and luster, which voluntarily lose their electrons to form cations. The distribution of metals in the environment is governed by the properties of the metal and influences of environmental factors.

Heavy metals are defined as metallic elements that have a relatively high density compared to water. With the assumption that heaviness and toxicity are inter-related, heavy metals also include metalloids, such as arsenic, that are able to induce toxicity at low level of exposure. In recent years, there has been an increasing ecological and global public health concern associated with environmental contamination by these metals.

Also, human exposure has risen dramatically as a result of an exponential increase of their use in several industrial, agricultural, domestic and technological applications Reported sources of heavy metals in the environment include geogenic, industrial, agricultural, pharmaceutical, domestic effluents, and atmospheric sources. Environmental pollution is very prominent in point source areas such as mining, foundries and smelters, and other metal-based industrial operations.

Although heavy metals are naturally occurring elements that are found throughout the earth's crust, most environmental contamination and human exposure result from anthropogenic activities such as mining and smelting operations, industrial production and use, and domestic and agricultural use of metals and metal-containing compounds. Environmental contamination can also occur through metal corrosion, atmospheric deposition, soil erosion of metal ions and leaching of heavy metals, sediment resuspension and metal evaporation from water resources to soil and ground water.

Natural phenomena such as weathering and volcanic eruptions have also been reported to significantly contribute to heavy metal pollution . Industrial sources include metal processing in refineries, coal burning in power plants, petroleum combustion, nuclear power stations and high tension lines, plastics, textiles, microelectronics, wood preservation and paper processing plants.

It has been reported that metals such as iron (Fe), chromium (Cr), and nickel (Ni) are essential nutrients that are required for various biochemical and physiological functions. Inadequate supply of these micro-nutrients results in a variety of deficiency diseases or syndromes. Some analytical methods such as atomic absorption spectrometry (AAS), electro thermal atomic absorption spectrometry (ETAAS), inductively couple plasma optical emission spectrometry (ICP-OES), and inductively couple plasma mass spectroscopy (ICP-MS) are employed for fast, accurate, and repeatable analysis of heavy metals in various samples. In the present work we have chosen the AAS, which is widely used due to its good precision, selectivity, low cost, and simplicity.

Of the 92 naturally occurring elements, approximately 30 metals and metalloids are potentially toxic to humans, Be, B, Li, Al, Ti, V, Cr, Mn, Co, Ni, Cu, As, Se, Sr, Mo, Pd, Ag, Cd, Sn, Sb, Te, Cs, Ba, W, Pt, Au, Hg, Pb, and Bi. Heavy metals is the generic term for metallic elements having an atomic weight higher than 40.04 (the atomic mass of Ca).

Although some individuals are primarily exposed to these contaminants in the workplace, for most people the main route of exposure to these toxic elements is through the diet (food and water). The contamination chain of heavy metals almost always follows a cyclic order: industry, atmosphere, soil, water, foods and human. Although toxicity and the resulting threat to human health of any contaminant are, of course, a function of concentration, it is well-known that chronic exposure to heavy metals and metalloids at relatively low levels can cause adverse effects.

Therefore, there has been increasing concern, mainly in the developed world, about exposures, intakes and absorption of heavy metals by humans. Populations are increasingly demanding a cleaner environment in general, and reductions in the amounts of contaminants reaching people as a result of increasing human activities. A practical implication of this trend, in the developed countries, has been the imposition of new and more restrictive regulations.

Industrial development include setting up of new industries and expansion of existing ones which resulted in the generation of toxic industrial effluents, that is often times discharged or released untreated to the environment leading to air, water, soil and soil solid waste pollution. Wastewater treatment is not given the necessary priority it deserves and therefore, industrial waste and domestic sewage are discharged into receiving water bodies without treatment. The consequence of this is increased pollution, loss of aquatic life and uptake of polluted water by plants and animals, which eventually gets into human body resulting in health related problems.

In the third world, many surface waters are known locally to be very contaminated but these cases are rarely documented, due to lack of basic tools such as established monitoring network as well as logistical and analytical capacities .

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